Spin Trapping Of Radicals Research Articles

A metal-organic framework (MOF) and graphene oxide (GO) based peroxymonosulfate (PMS) activator applied in pollutant removal

Fenton-like reactions based on the peroxymonosulfate (PMS) can efficiently degrade pollutants and have attracted widespread attention. Herein, we reported a facile strategy to synthesize a heterogeneous PMS activator (Zn/Co-MOF@rGO-600) derived from a cobalt-zinc bimetallic metal-organic framework (MOF). The Zn/Co-MOF@rGO-600 was applied as the catalyst for the effective tetracycline (TC) removal during the PMS activation process. The introduction of Zn and the presence of graphene oxide (GO) not only enhanced the yield of the single-atom cobalt (Co0) in the catalyst through the bimetallic synergy but also had a positive effect on adjusting the morphology of the catalyst. The charge transfer resistance (Rct) of Zn/Co-MOF@rGO-600 decreased by 3.15 times after GO modification. The reaction rate constant (k) increased by 14.88 times in the reaction system with Zn/Co-MOF@rGO-600 as PMS activator, the corresponding efficiencies of TC removal and mineralization increased to 91.66 % and 45.04 %, respectively. Density functional theory (DFT) calculation suggested that the bonding energy (Ebon) between PMS and the Zn-Co atom was low enough to − 2.76 eV so that the Zn/Co-MOF@rGO-600 could act as an effective PMS activator. The quenching experiment and the radical spin trap test showed the main generated reactive species were SO4•-, O2•- and 1O2. The presence of SO4•- was the main driving factor for the generation of other radicals such as 1O2 and •OH during the PMS activation process. This research proposes a new reference to fabricate an effective catalyst for PMS activation, which was derived from a bimetallic (Zn/Co) MOFs.

Trace amounts of mercaptans with key roles in forming an efficient three-component photoinitiation system for holography

Investigating the photoinitiation mechanisms will help to find new directions for high-efficiency photoinitiation systems (PS). This article aimed to explore other possible roles of mercaptans in a PS where mercaptans were widely regarded as chain transfer agents. A bis-chalcone dye (BDEA) and a biimidazole (HABI) were employed as photosensitizer and co-initiator, and 2-mercaptobenzoxazole (MBO) was chosen as a representative of mercaptans. Trace amounts of mercaptans have been shown a negligible chain transfer effect in previous research studies, but in this work, they were found a miraculous ability to significantly promote the diffraction efficiency. Besides, the diffraction efficiency showed an interesting trend of first increasing and then decreasing with the increase of MBO content. The diffraction behavior was subsequently confirmed to be closely correlated with photoinitiation efficiency by monomer polymerization kinetics. Therefore, we made many efforts to detect the photoinitiation mechanism of PS and the roles of mercaptans. Combining the thermodynamic feasibility analysis with the spin trapping of free radicals, the presence of mercaptans could make the PS evolve a double-cycle photoreaction, which was considered to be an important contribution to the obvious promotion of photoinitiation efficiency. Meanwhile, considering the results of the fluorescence and absorption spectra, the static quenching between BDEA and MBO was presumed to be the factor of the decline in photoinitiation efficiency. Finally, the optimized photopolymers exhibited good performance in recording and reproducing reflection holograms.

On 'Spin trapping of superoxide and hydroxyl radical: Practical aspects' by Eli Finkelstein, Gerald M. Rosen and Elmer J. Rauckman

This commentary describes a highly cited paper by Eli Finkelstein, Gerald M. Rosen, and Elmer J. Raukman that appeared in Archives of Biochemistry and Biophysics published in 1980. They reviewed many reports being regularly appearing in the literature describing spin trapping and hydroxyl radicals from various sources and contributed to the development and progress that has been made in oxidative stress research.

Publisher notice

This commentary describes a highly cited paper by Eli Finkelstein, Gerald M. Rosen, and Elmer J. Raukman that appeared in Archives of Biochemistry and Biophysics published in 1980. They reviewed many reports being regularly appearing in the literature describing spin trapping and hydroxyl radicals from various sources and contributed to the development and progress that has been made in oxidative stress research.

Hybrid PVDF-P(L-DOPA)-ZnO membranes for dyes and antibiotics removal through simultaneous action of adsorption and photocatalysis processes

PVDF-P(L-DOPA)-ZnO hybrid membranes were prepared with the purpose to eliminate several classes of pollutants from water: cationic dyes and antibiotics. The PVDF membrane with the pores mean size of 1.5 µm was prepared by the phase inversion method. P(L-DOPA), a PDA analogue, was deposited on the polymeric membrane to facilitate the anchor of in-situ grown ZnO nanoparticles. Several characterization methods were deployed to explore the hybrid membranes' structural, morphological, optical, and photocatalytic properties. The firm P(L-DOPA)-ZnO coating on the PVDF membrane surface converted its hydrophobic nature to a hydrophilic one. For an optimal ZnO nanoparticles amount and size, efficient degradation of Rhodamine B (RhB- 80%) and oxytetracycline (OTC-71%) was obtained in 5 h of UV-light irradiation. The generation of P(L-DOPA)-ZnO Z-scheme photocatalyst promotes an efficient separation of photoinduced electron-hole pairs beneficial to photocatalytic activity. The hybrid membrane revealed similar photocatalytic activity after 3 cycles illustrating high stability. The analysis of the generated reactive oxygen species correlated with radical spin trapping experiments suggest that photogenerated h+ play the main role in the photodegradation of both studied pollutants.

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Novel mechanisms in alcohol neurodevelopmental disorders via BRCA1 depletion and BRCA1-dependent NADPH oxidase regulation

The breast cancer 1 protein (BRCA1) facilitates DNA repair, preventing embryolethality and protecting the fetus from reactive oxygen species (ROS)-induced developmental disorders mediated by oxidatively damaged DNA. Alcohol (ethanol, EtOH) exposure during pregnancy causes fetal alcohol spectrum disorders (FASD), characterized by aberrant behaviour and enhanced ROS formation and proteasomal protein degradation. Herein, ROS-producing NADPH oxidase (NOX) activity was higher in Brca1 +/− vs. +/+ fetal and adult brains, and further enhanced by a single EtOH exposure. EtOH also enhanced catalase and proteasomal activities, while conversely reducing BRCA1 protein levels without affecting Brca1 gene expression. EtOH-initiated adaptive postnatal freezing behaviour was lost in Brca1 +/− progeny. Pretreatment with the free radical spin trap and ROS inhibitor phenylbutylnitrone blocked all EtOH effects, suggesting ROS-dependent mechanisms. This is the first in vivo evidence of NOX regulation by BRCA1, and of EtOH-induced, ROS-mediated depletion of BRCA1, revealing novel mechanisms of BRCA1 protection in FASD.

A Critical Review on Removal of Gaseous Pollutants Using Sulfate Radical-based Advanced Oxidation Technologies.

Excessive emissions of gaseous pollutants such as SO2, NOx, heavy metals (Hg, As, etc.), H2S, VOCs, etc. have triggered a series of environmental pollution incidents. Sulfate radical (SO4•-)-based advanced oxidation technologies (AOTs) are one of the most promising gaseous pollutants removal technologies because they can not only produce active free radicals with strong oxidation ability to simultaneously degrade most of gaseous pollutants, but also their reaction processes are environmentally friendly. However, so far, the special review focusing on gaseous pollutants removal using SO4•--based AOTs is not reported. This review reports the latest advances in removal of gaseous pollutants (e.g., SO2, NOx, Hg, As, H2S, and VOCs) using SO4•--based AOTs. The performance, mechanism, active species identification and advantages/disadvantages of these removal technologies using SO4•--based AOTs are reviewed. The existing challenges and further research suggestions are also commented. Results show that SO4•--based AOTs possess good development potential in gaseous pollutant control field due to simple reagent transportation and storage, low product post-treatment requirements and strong degradation ability of refractory pollutants. Each SO4•--based AOT possesses its own advantages and disadvantages in terms of removal performance, cost, reliability, and product post-treatment. Low free radical yield, poor removal capacity, unclear removal mechanism/contribution of active species, unreliable technology and high cost are still the main problems in this field. The combined use of multiactivation technologies is one of the promising strategies to overcome these defects since it may make up for the shortcomings of independent technology. In order to improve free radical yield and pollutant removal capacity, enhancement of mass transfer and optimization design of reactor are critical issues. Comprehensive consideration of catalytic materials, removal chemistry, mass transfer and reactor is the promising route to solve these problems. In order to clarify removal mechanism, it is essential to select suitable free radical sacrificial agents, probes and spin trapping agents, which possess high selectivity for target specie, high solubility in water, and little effect on activity of catalyst itself and mass transfer/diffusion parameters. In order to further reduce investment and operating costs, it is necessary to carry out the related studies on simultaneous removal of more gaseous pollutants.

Electrochemical Oxidative [4+2] Annulation of Different Styrenes toward the Synthesis of 1,2-Dihydronaphthalenes

Electrochemical Oxidative [4+2] Annulation of Different Styrenes toward the Synthesis of 1,2-Dihydronaphthalenes

The mechanism of action and modified synthesis of hydroxyurea

Searching of new drugs with antimitotic characteristics which can be used for decreasing of cancer cells dividing is the important issue of nowadays. One of such substances there is a hydroxyurea (HU) that is known as mitotical poison, because of characteristic to block a cellular cycle and as the specific inhibitor of DNA synthesis. It blocks the transition of cells from G1 – in S-phase. HU is a cytostatic agent with antineoplastic activity and presents great clinical efficiency in the treatment of sickle cell disease. HU and its derivatives exhibit versatile biological activities. HU is currently used in the treatment of various neoplastic and non-neoplastic diseases such as cancer, sickle cell anemia and HIV.Currently anticancer drugs are available that significantly reduce the mortality rates for some cancers (e.g. leukemia and testicular and ovarian cancer), and give longer overall patient survival times. In order to drug belongs to the pharmacotherapeutic group – antineoplastic agents and widely used for myelogenous leukemia, essential thrombocythemia treatment, our research was concerning the literature review on the ways and mechanisms of action of HU in living organisms. The ways and mechanisms of HU action in living organisms, research of antiviral and antimicrobial action of HU, the mechanism of HU influence at the cellular level and in antitumor and anticancer therapy have been studied. Under studying of radioprotector properties of hydroxyurea was established, that its efficiency is estimated by the values FCD (Factor of change of dose) within the limits of 1.2–1.4 – (to the peas 1.4 and corn – 1.3). A factor of change of dose is a relation of effective dose at the irradiation of organism with a radioprotector to the effective dose that predetermines the same radio-biology effect in control without a radioprotector. It was established that compounds with sulfurhydryl bonding possess the most radioprotective properties. It is considered that they have strong reduction properties and can be used as spin trapping of free radicals, shutting them out before binding with macromoleculas occurs, in particular to DNA. In order to obtain a sufficient amount of the drug hydroxyurea for analytical and pharmacological research, a modified method of it synthesis has been developed and proposed. The optimized synthesis conditions include conducting the experiment at lower temperatures -15 °C (wise -10 °C lit.), neutralization of the reaction mixture with concentrated 50 % sulfuric acid (wise dilute sulfuric acid, lit.); providing concentrated solution by reducing the total amount of water in the reaction 300 ml (wise 500 ml); evaporation and the filtration at room temperature by air flow (wise evaporation in vacuum at 40 °C, lit.); replacement of the solvent for extraction with butanol ( wise alcohol, lit.). Such conditions provided complete dissolution of urethane after 1 h and allow to receive the hydroxyurea pure enough, without further recrystallization. The target product was obtained with a higher yield (up to 91 %) and achieved simplicity and one-step method. The less toxic and cost-effective starting reagents were also used to reduce the cost of the synthesis process.

Evaluation of PBN spin-trapped radicals as early markers of lipid oxidation in mayonnaise

Quality deterioration of mayonnaise is caused by lipid oxidation, mediated by radical reactions. Assessment of radicals would enable early lipid oxidation assessment and generate mechanistic insights. To monitor short-lived lipid-radicals, N-tert-butyl-α-phenylnitrone (PBN), a spin-trap, is commonly used. In this study, the fate of PBN-adducts and their impact on lipid oxidation mechanisms in mayonnaise were investigated. The main signals detected by Electron Spin Resonance (ESR) were attributed to L-radicals attached to 2-methyl-2-nitrosopropane (MNP), one of three degradation products of the PBN-peroxy-adduct. The second degradation product, benzaldehyde, was detected with Nuclear Magnetic Resonance (1H NMR), in line with MNP-L adduct generation. For the third class of degradation products, LO-radicals, their scission products were detected with 1H NMR and indicated that LO-radicals have a major impact on downstream oxidation pathways. This precludes mechanistical studies in presence of PBN. Degradation products of PBN-adducts can, however, be used for early assessment of antioxidants efficacy in oil-in-water emulsions.

Application of persulfate with hydrodynamic cavitation and ferrous in the decomposition of pentachlorophenol.

Hydrodynamic cavitation (HC) and Fe(II) are advanced oxidation processes, in which pentachlorophenol (PCP) is treated by the redox method of activating persulfate (PS). The kinetics and mechanism of the HC and Fe(II) activation of PS were examined in aqueous solution using an electron spin resonance (ESR) spin trapping technique and radical trapping with pure compounds. The optimum ratio of Fe(II)/PS was 1:2, and the hydroxyl radical (HO) and sulfate radical (SO4-) generation rate were 5.56mMh-1 and 8.62μMh-1, respectively. The generation rate and Rct of HO and SO4- at pH 3 and 50°C in the Fe(II)/PS/HC system are 7584.6μMh-1, 0.013 and 24.02μMh-1, 3.95, respectively. The number of radicals was reduced as the pH increased, and it increased with increasing temperature. The PCP reaction rate constants was 4.39×10-2min-1 at pH 3 and 50°C. The activation energy was 10.68kJmol-1. In addition, the mechanism of PCP treatment in the Fe(II)/PS/HC system was a redox reaction, and the HO-/SO4- contribution was 81.1 and 18.9%, respectively. In this study, we first examined PCP oxidation through HO and SO4- quantification using only the Fe(II)/PS/HC process. Furthermore, the results provide the foundation for activation of PS by HC and Fe(II), but also provide a data basis for similar organic treatments other than PCP.

Superoxide and Hydroperoxyl Radical Spin Trapping Using 5,5- Dimethyl-1-Pyrroline N-Oxide in Dehydrated N,N-Dimethylformamide

Herein, superoxide radical (O2•−) spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in dehydrated N,N-dimethylformamide (DMF) solution is investigated via electrochemistry and electron spin resonance (ESR) measurements supported by theoretical calculations. In aprotic environments, DMPO gradually reacts with electrogenerated O2•−; however, the trapping kinetics are considerably slow and cannot enable successful radical trapping in aqueous biological experiments. Alternatively, adding a proton source changes the voltammetric behavior, rendering the detection of the spin adduct easy with ESR. These results suggest that the proton addition to O2•−, which forms a hydroperoxyl radical (HO2•), accelerates the kinetics of radical trapping. Accordingly, we propose that the actual target of DMPO spin trapping is HO2• rather than O2•−.

Enhanced Transformation of Emerging Contaminants by Permanganate in the Presence of Redox Mediators.

In this study, a permanganate/redox mediator system for enhanced transformation of a series of emerging contaminants was evaluated. The presence of various redox mediators (i.e., 1-hydroxybenzotriazole, N-hydroxyphthalimide, violuric acid, syringaldehyde, vanillin, 4-hydroxycoumarin, and p-coumaric acid) accelerated the degradation of bisphenol A (BPA) by Mn(VII). Since 1-hydroxybenzotriazole (HBT) exhibited the highest reactive ability, it was selected to further investigate the reaction mechanisms and quantify the effects of important reaction parameters on Mn(VII)/redox-mediator reactions with BPA and bisphenol AF (BPAF). Interestingly, not only HBT accelerated the degradation of BPA, but also BPA enhanced the decay of HBT. Evidence for the in situ formation of HBT· radicals as the active oxidant responsible for accelerated BPA and BPAF degradation was obtained by radical scavenging experiments and 31P NMR spin trapping techniques. The routes for HBT· radical formation involving Mn(VII) and the electron-transfer pathway from BPA/BPAF to HBT· radicals demonstrate that the Mn(VII)/HBT system was driven by the electron-transfer mechanism. Compared to Mn(VII) alone, the presence of HBT totally inhibited self-coupling of BPA and BPAF and promoted β-scission, hydroxylation, ring opening, and decarboxylation reactions. Moreover, Mn(VII)/HBT is also effective in real waters with the order of river water > wastewater treatment plant (WWTP) effluent > deionized water.

3.2.7 Spin Trapping of Radicals in Methanol Solution Irradiated by Heavy Ion Beams—Effect of Specific Energy and LET—

3.2.7 Spin Trapping of Radicals in Methanol Solution Irradiated by Heavy Ion Beams—Effect of Specific Energy and LET—

Embedding cyclic nitrone in mesoporous silica particles for EPR spin trapping of superoxide and other radicals

The generation of superoxide radical anion in biological systems is one of the major initiating events in the redox biology of NADPH oxidases and mitochondrial redox signalling. However, the pallette of chemical tools for superoxide detection is very limited, hampering progress in understanding the chemical biology of superoxide. Although EPR spin trapping is regarded as the most rigorous technique for superoxide detection, rapid reduction of the EPR-active superoxide spin adducts to EPR-silent hydroxylamines, or to hydroxyl radical adducts by bioreductants, significantly limits the applicability of this technique in biological systems. To overcome these limitations, in this work, we report the synthesis and characterization of a new mesoporous silica functionalized with a phosphorylated cyclic spin trap (DIPPMPO nitrone). The DIPPMPO-grafted silica is a versatile spin-trap agent enabling the identification of a wide range of carbon or oxygen-centered transient radicals in organic and in aqueous media. Moreover, superoxide was efficiently trapped under in vitro conditions in both cell-free and cellular systems. The generated superoxide adduct exhibited an exceptional half-life of 3.5 h and a resistance toward bioreductant agents such as glutathione for several hours.

Measurement of OH* Generation by Pulverized Minerals Using Electron Spin Resonance Spectroscopy and Implications for the Reactivity of Planetary Regolith.

Mineral analogs to silicate phases common to planetary regolith, including olivine; the pyroxenes augite and diopside; the plagioclase feldspars labradorite, bytownite, and albite; the Johnson Space Center‐1A lunar regolith simulant; as well as quartz (used as a reference), were subjected to mechanical pulverization by laboratory milling for times ranging from 5 to 45 min. Pulverized minerals were then incubated in an aqueous solution containing the free radical spin trapping compound 5,5‐Dimethyl‐1‐Pyrroline‐N‐Oxide for times ranging from 5 to 30 min. These slurries were then analyzed by Electron Paramagnetic Resonance spectroscopy to quantify the amount of hydroxyl radical (the neutral charge form of the hydroxide ion, denoted as OH*) formed in solution. We find that all tested materials generate an Electron Paramagnetic Resonance spectrum indicating the formation of OH* with concentrations ranging between 0.1 and 1.5 μM. We also find that, in general, mineral pulverization time is inversely correlated to OH* generation, while OH* generation is positively correlated to mineral fluid incubation time for phases that have iron in their nominal chemical formulae, suggesting the possible action of Fenton reaction as a cofactor in increasing the reactivity of these phases. Our results add to a body of literature that indicates that the finely comminuted minerals and rocks present in planetary regolith are capable of generating highly reactive and highly oxidizing radical species in solution. The results provide the foundation for further in vitro and in vivo toxicological studies to evaluate the possible health risks that future explorers visiting the surfaces of planetary bodies may face from these reactive regolith materials.

P-226 - An unexpected free radical mechanism for DNA damage by the carcinogenic arylhydroxamic acid via sunlight irradiation

The carcinogenicity of N-hydroxy-2-acetamidofluorene (N-OH-AAF), the major genotoxic metabolite of classic model aromatic amine carcinogen 2-acetylaminofluorene (AAF), has been attributed mainly to the formation of DNA adducts via reactive arylnitrenium ion upon further enzymatic activation. Here we show, unexpectedly, that exposure of N-OH-AAF to UV and sunlight irradiation induced the formation of the well-known DNA adducts; but more interestingly, simultaneous oxidative DNA damage was also observed as measured by the formation of DNA single/double strand breaks and 8-oxodG, which were inhibited by the typical •OH scavengers (DMSO and ethanol). ESR secondary radical spin-trapping and fluorescent studies unequivocally confirmed that •OH was generated from N-OH-AAF photolysis. We propose that the highly reactive •OH and amidyl radicals can be readily produced via homolysis N-O in N-OH-AAF by UV and sunlight, which can induce both oxidative DNA damage and formation of DNA adducts. This represents the first report of •OH production and DNA damage via photo-activation of the genotoxic raylhydroxamic acid intermediate, which may provide a new perspective to understand the molecular mechanism for the carcinogenicity of aromatic amines.

Fabrication of microstructured binary polymer brush "corrals" with integral pH sensing for studies of proton transport in model membrane systems.

Binary brush structures consisting of poly(cysteine methacrylate) (PCysMA) "corrals" enclosed within poly(oligoethylene glycol methyl ether methacrylate) (POEGMA) "walls" are fabricated simply and efficiently using a two-step photochemical process. First, the C-Cl bonds of 4-(chloromethyl)phenylsilane monolayers are selectively converted into carboxylic acid groups by patterned exposure to UV light through a mask and POEGMA is grown from unmodified chlorinated regions by surface-initiated atom-transfer radical polymerisation (ATRP). Incorporation of a ratiometric fluorescent pH indicator, Nile Blue 2-(methacryloyloxy)ethyl carbamate (NBC), into the polymer brushes facilitates assessment of local changes in pH using a confocal laser scanning microscope with spectral resolution capability. Moreover, the dye label acts as a radical spin trap, enabling removal of halogen end-groups from the brushes via in situ dye addition during the polymerisation process. Second, an initiator is attached to the carboxylic acid-functionalised regions formed by UV photolysis in the patterning step, enabling growth of PCysMA brushes by ATRP. Transfer of the system to THF, a poor solvent for PCysMA, causes collapse of the PCysMA brushes. At the interface between the collapsed brush and solvent, selective derivatisation of amine groups is achieved by reaction with excess glutaraldehyde, facilitating attachment of aminobutyl(nitrile triacetic acid) (NTA). The PCysMA brush collapse is reversed on transfer to water, leaving it fully expanded but only functionalized at the brush-water interface. Following complexation of NTA with Ni2+, attachment of histidine-tagged proteorhodopsin and lipid deposition, light-activated transport of protons into the brush structure is demonstrated by measuring the ratiometric response of NBC in the POEGMA walls.

Development of a reactive oxygen species-sensitive nitric oxide synthase inhibitor for the treatment of ischemic stroke.

Ischemic stroke is caused by a blockage of cerebral blood flow resulting in neuronal and glial hypoxia leading to inflammatory and reactive oxygen species (ROS)-mediated cell death. Nitric oxide (NO) formed by NO synthase (NOS) is known to be protective in ischemic stroke, however NOS has been shown to 'uncouple' under oxidative conditions to instead produce ROS. Nitrones are antioxidant molecules that are shown to trap ROS to then decompose and release NO. In this study, the nitrone 5 was designed such that its decomposition product is a NOS inhibitor, 6, effectively leading to NOS inhibition specifically at the site of ROS production. The ability of 5 to spin-trap radicals and decompose to 6 was observed using EPR and LC-MS/MS. The pro-drug concept was tested in vitro by measuring cell viability and 6 formation in SH-SY5Y cells subjected to oxygen glucose deprivation (OGD). 5 was found to be more efficacious and more potent than PBN, and was able to increase phospho-Akt while reducing nitrotyrosine and cleaved caspase-3 levels. 6 treatment, but not 5, was found to decrease NO production in LPS-stimulated microglia. Doppler flowmetry on anesthetized mice showed increased cerebral blood flow upon intravenous administration of 1mg/kg of 5, but a return to baseline upon administration of 10mg/kg, likely due to its dual nature of antioxidant/NO-donor and NOS-inhibition. Mice treated with 5 after permanent ischemia exhibited a >30% reduction in infarct volume, and higher formation of 6 in ischemic tissue resulting in region specific effects limited to the infarct area.